Magnetic core for inductance-coils.



BEST AVNLABLE COP:

,No. 705,935. Patented July-29, I902. .1; 1;. LEE & E. u. COLPITTS.MAGNETIC CORE FOB lNDUCTANtE COILS.

(Apgliution filed Nov. 80, 1901.) (No Model.) 7 2 Sheots-'-Sheet- I.

W'ITNESSES BEST AVNLABLE COPX Patentd lul zs, 4902.

I No. 705,935.

J. C. LEE &. E. H. COLPITTS.

MAGNETIC CUBE FOR INDUCTAHCE GDILS.

(Application filed lffov. 30, 1901.)

2 Sheets-Sheet 2 (lo Iodel.)

[N VEN T0125 BEST A UNITED STATES VAiLABLE CGP";

PATENT OFFICE.

JOHN C. LEE, OF' BROOKLINE, AND E DWIN'II. COLPITTS, on BOSTON, MAS-COMPANY, A CORPORATION OF NEW YORK.

MAGNETIC CORE FOR INDUC TANCE-COILS.

SPECIFICATION o m g p t of Letters Patent No. 705,935, dated July 29,1902. Application filed November 30, 1901. Serial No. 84,199. (Nomodel.)

To all whom it may concern.-

Be it known that we, JOHN 0. LEE, residing at Brookline, in. the countyof Norfolk, and EDWIN H. OOLPITTS, residing at Boston,

in the county of Suffolk, State of Massachusetts, have invented certainImprovements in Magnetic Cores for Ind uctance-Ooils, of which thefollowing is a specification.

This invention relates to self -induction 1o coils such as are employedin loading electric circuits, and more particularly concerns themagnetic cores employed in conjunction with the electrical winding ofsuch coils and constituting wholly or in part the magnetic circuitsthereof.

Two main requirements of a loading-coil are that the resistance of itswinding shall be low and that its inductance shall be high, and it isevident that the easiest and most prac- 2o tical way of attaining thesequalifications is to provide the coil with a core formed of materialpossessing high magnetic permeability, since the magnetic circuit of thecoil is thereby shortened, its field intensified, and its actionexalted, so that the required inductance may be obtained with a smallernumber of turns of the copper winding, and the coil consequently mademuch smaller than otherwise would be possible.

Heretofore the magnetic cores of loading or inductance coils and, infact, also of induction-coils and other electromagnetic apparatus havebeen formed exclusively of metallic iron, and as concerns permeabilitythe use of 3 5 iron as a material forsuch cores leaves little to bedesired; but when coils containing iron cores are employed in circuitwhere, as in telephone-circuits, the periodicity of the currenttraversing the coil-winding is high it becomes 0 evident that theconductivity of the iron is a disadvantageous attribute thereof, sinceit facilitates the generation and development of parasitic or eddycurrents in the conductive substance of the core, involving a fruitlessa 1d wasteful expenditure of the available e, trical energy of thecircuit, indicated by an :ndue and abnormal fall of potential in thecoil or by an excessive apparent resistance between the terminalsthereof, the said by rolling up an iron eddy-currents in the core beingdeveloped at the expense of losses in the working current of thecircuit, which is correspondingly weakened.

To reduce the conductivity of iron cores or to increase their resistancein the plane of the electromagnetic convolutions surrounding them, andthereby to reduce eddy-currents, and thus avoid as far as possible thelosses they represent, it is customary in practice to laminate suchcores or in other ways to divide their iron in planes parallel to thedirection of magnetization andto insulate the several component plates,strips, or wires of such a divided core from one another; but losses sosmall as to be negligible when Occurring in electromagnetic coils usedin connection with heavy currents and with the relatively lowperiodicity prevailing in the commercial employment of such currentsfrequently exercise a seriously adverse elfect when found intelephone-circuits, wherein the conditions of transmission, includingthe exceptional feebleness and the extremely high periodicity of theaverage working current, are essentially different from those of anyother system, and in loading-coils for telephonic circuits in orderthatthe core losses may be sufiiciently reduced it has been foundexpedient to divide the iron of the cores to the most radical extent,having each separate element 8o as thin as possible, and to insulate theseveral component members of said cores with greater care andthoroughness than has in other classes of coil been necessary. Cores forloading-coils have thus been made both ribbon and by winding lI'Oll wireinto the form of a torus, the metal of the ribbon having a thickness ofbut .00175 of an inch, while the thickness of the wire employed was but.003965 of an inch, the said 0 wire being that known as No. 38 Brown andSharpe gage. The ribbon used was insulated on both sides,and the wirewhen employed was carefully and thoroughly insulated, so that each turnthereof when formed into the ringcore was completely insulated from allother turns. The red uction of iron ribbon and wire to such anattenuated thickness and size is,

BESTAVAlMBLE COP:

however, very expensive, and to perfectly and continuously insulateribbon or wire so reduced is both expensive and diiiicult.

The objects of this invention therefore are to providea practicalsubstitute for iron finely divided and insulated in the above-describedmanner as a material for the cores of inductance or loading coils fromwhich cores capable of giving substantially improved effects or resultscan be made at less cost and the ready production from such substitutematerial of loading-coil cores of proper or suitable form.

It has been discovered that magneticoxids possess these characteristicsand that ferroso-ferric oxid (Fe O or magnetic oxid of iron inparticular is well qualified for use as a material for the cores ofloading-coils, provided that some practical way can be devised forworking it, for bringing it into and enabling it to retain such shapeand form as to be commercially serviceable, and for maintainingpractical continuity in the direction of magnetization.

Tothis end the invention comprehends a method or process for theproduction of practical and suitable inductance or loading coilcores ofmagnetic oxid and a non-conducting, highly permeable, compact and solidcore produced by said method. In the production of cores by the saidmethod thin plates or ribbons or very small Wire of magnetic metal areassembled, lapped, or wound into a loosely-built or partly open-workstructure of any proper or desired conformation, and the said structureor core-form isjthen subjected to the roasting action of heat in anatmosphere capable of yielding oxygen to the metal of which it iscomposed until said metal is reduced or converted into magnetic oxid.This conversion is greatly facilitated by the loose or open-workarrangement of the structure, which aifords the said oxygen-yieldingatmosphere ready access to the interior surfaces of the metallic massand enables the oxidation to be effected throughout the said mass andnot merely on the exterior thereof, and a practical way of securing thedesired supply of such an oxygen-imparting atmosphere is to admit steamor other convenient medium, such as air or carbon dioxid, which willreadily give up oxygen to the metal, through a jet into theroasting-oven or inuilie containing the core-form during the continuanceof the oxidizing process. The core thus made is composed of artificialmagnetic oxid and while retaining the form in which it was originallyconstructed has become dense and compact, its substance during theroasting operation having experienced internal enlargement, or,otherwise stated, its interstices or open-work interior spaces havingbeen gradually filled up by the expansion into them of the core materialas its conversion into magnetic oxid has progressed. Moreover, it is acore which with sufficient magnetic permeability combines extremely highspecific electrical resistance, and therefore has no tendency to serveas a circuit for the formation and development of eddy-currents.

In the drawings which accompany and illustrate this specification,Figures 1, 2, 3, 4, and 5 concern a core initially prepared by windingwire of magnetizable metal, such as iron, into the form desired. Figs.1, 2, and 3 are respectively a side view, a central cross-section, and aperspective view thereof, a portion of the covering in Figs. 1 and 3being removed to show the appearance of the wire as laid up. Fig. 4represents a straight piece of such wire, and Fig. 5 shows two suchsections crimped or crinkled and laid up parallel to one another toillustrate the open-work relation of two adjacent turns when wound intoproper form. Figs. 6 and 7 are side and sectional views, respectively,of a core-form made by windingor rolling upastrip or ribbon of the saidmagnetic metal; and Figs. Sand 9 representface and edge views ofsucharibbon. Figs. 10 and 11 are respectively side and sect-ional viewsof a third initial construction, showing a core-form prepared bybuilding plates of magnetic metal; and Figs. 12 and 13 are front andedge Views of a portion of the plates. Figs. 14 and 15 are side andsectional views of a drum upon which the wire or ribbon may be wound andthe plates piled or built up into the core-formdesired. Fig. 16illustrates the manner of oxidizing the prepared coreforms by heating orroasting them in a suitable chamber or mufile and means for introducingthe oxygen-containing medium to said chamber, and Fig. 17 represents aportion of an electric circuit provided with loading-coils containingmagnetic cores of the character described herein.

Referring to the drawings, A in Figs. 1 and 3 represents a finishedring-core initially prepared or built of iron wire 10, wound to thedesired form or shape and size. The size of wire employed may be variedwithin a considerable range, and Fig. 4 may be regarded as indicatinggenerally a size which will be found suitable. In core-forms which wehave made wire having a diameter of sixteen millimeters has been usedand found satisfactory. Since such core-forms are preferably to beoxidized throughout, it is advisable, in order to facilitate oxidation,that the elements or turns thereof shall be laid up in such manner as tohave some slight separation from one another, and thus to constitute aloosely-built mass or partly open-work structure having intersticesbetween its several elements in such communication by suitable channelswith the outside of the mass as to afford the oxidizing agency oroxygen-giving atmosphere ready access to the interior surfaces. In thepresent instance of cores prepared by winding iron wire the desiredseparation is attained by employing crimped or crinkled wire, asindicated by Fig. 5 and at the parts 705,935 BEST AVAltABLE com of Figs.1 and 3 where the covering 0 of the finished core is shown as havingbeen re moved.

Ribbons or strips of iron may be employed in place of wire in thepreparation of the coreforms. Such a construction is represented byFigs. 6, 7, 8, and 9, wherein 1" indicates the said ribbon, a portionthereof being shown separately in Fig. 8. The ribbon is wound or laid upspirally, as shown in the sectional View Fig. 7 and in Fig. 6 at thatpart of the core A from which the covering has been stripped.

Another alternative plan of preparing the core-forms initially isto;employ thin ringshaped plates or sheet-iron rings built or piled uponone another. Fig. 12 represents a portion of such a plate 19, and Fig.13 indicates the way in which the said plates 19 are built up into theform desired. The open-work arrangement or desired separation of thelayers or turns in the core-forms prepared-from iron tape or sheet-ironrings may readily be attained, as indicated in Figs. 8, 9, 12, and 13,by prick-punches or like indentations j, these urnishing a number ofprojections between each two approximating surfaces and acting to keepsuch surfaces apart during the earlier stages of the oxidizingoperation.

The convolutions or layers of the several core-forms prepared by eitherplan may be held in place and the form of the core thereby maintained bymeans of stout binding-wires W, any desired number of which may bethreaded through the central opening and brought around to-the outside,where the two ends of each such wire may then be twisted together, as att.

Figs. 14: and 15 indicate a form of drum which may conveniently beemployed in the preparation of the wire and tape core-forms, and, ifdesired, in preparing the sheet-iron ring core-form also. The said drummay consist of a hub h, a fixed flanged side B, attached thereto, and adetachable side 6, adapted to be secured to the hub by any suitabledevice, such as a screw and nut n. Radial slits or channels 5 are cut atopposite points in the flanged sides B and b at any preferred number ofpoints, and these are continued, as shown at 8 for a short distance intoand across the substance of the hub. These slits provide means forattaching the binding-wires W around the core-forms before the saidforms are taken from the drum or reel. The said binding-wires arereadily threaded through the depressions or grooves 8 which cross theperiphery of the hub, as indicated in Fig. 15, and may then be drawn uparound the sides of the iron mass and secured by twisting their endstogether at any outside point. .The core-forms prepared as described arethen heated or roasted by subjecting them to a proper temperature in thepresence of a constantlysupplied or renewed atmosphere capable ofyielding oxygen to 'the iron until the whole or the main part of theirmetallic substance is converted into magnetic or ferroso-ferric oxid. Incarrying out this operation we have, as illustrated in Fig.

16, placed one or more prepared metallic meability, we find it desirableto convert the 7 metal into magnetic oxid of practically uniformconstitution and without any considerable admixture or association oflower oxids, and for such uniform or substantially uniform conversionthe heating operation should preferably be continued for several days.

The roasting or oxidizing operation is not restricted to any precisedegree of heat and may be properly performed at any high temperaturewithin a comparatively wide range, varying from cherry red to brightorange or even white. We have, however, employed a bright cherry redwith good results, our coreforms when subjected thereto for periods oftime of from three days to one week having been found satisfactory.

When taken from the heating-chamber the cores are practically unchangedin conformation, but are greatly increased in weight, their substancehaving been transformed from iron to magnetic oxid, and they have becomesubstantially dense, compact, and coherent, the oxid formed interiorlyhav ing expanded into the spaces or interstices originally left betweenthe convolutions or layers. Cores of artificial magnetic oxid producedby this method are suficiently strong for all practical purposes, arecontinuous in the direction of magnetization, possess sulficientmagnetic permeability, and are of such high electrical resistance thatcore losses in inductance or loading coils with which they may beassociated are so slight that they may be disregarded. The said magneticoxid corcs when cooled may, if desired, be furnished with any suitablecovering c-such as a wrapping of strips of stifi paper. or linen whichmay be secured by a resinous or as phaltic cement or by strong cords orligaments e, which may pass through the central hole and around thesubstance of the core. The electrical winding may then be applied in anypreferred way. Fig. 17 shows one way in which the coils may be wound andcon nected with a working circuit. Two distinct coil-windings 3 and tmay be wound over opposite halves of the core in equal portions,separated from one another at the ends by the non-conducting partitionsg. The said two coil-windings may then be connected, as

BEST AVAiU BLE CC? t shown, in the two main conductors m '0,respectively, of the electric circuit L.

While this specification mainly contemplates the use of iron as amagnetizable material to be oxidized for the production of ourmagnetic-oxid cores and while iron being perfectly adapted for thepurpose is generally to be preferred, we desire to point out that theterm is not to be understood in any restricted sense and that we regardthe use of steel, nickel, alloys of iron and nickel, and other magneticmetals and alloys when employed to serve as the basis of magneticoxidcores as being within the spirit or scope of our invention.

In this application we have claimed the new core and the process ofmaking the same. In

our application filed of even date herewith, Serial N 0. 84,200, we havedescribed and claimed a loaded coil, as well as an electrical circuitfor the transmission of energy, of which the aforesaid core forms apart.

We claim 1. The herein-described method of producing non-conductingmagnetic cores for electromagnetic apparatus, which consists insubjecting divided magnetic metal assembled or laid up into aloosely-built or open-work mass of desired form to heat in an atmospherecapable of constantly yielding oxygen to the said metal, until the saidmass is substantially converted to magnetic oxid.

2. An improvement in the art of producing cores of high electricalresistance and sufficient permeability, for inductance or loading coils,which consists in building plates wires or like thin elements of ironinto proper form and size, and then submitting the same as a whole tothe action of a high temperature in the presence of an oxygen-yieldingatmosphere, until the iron is reduced or converted to ferroso-ferricoxid, substantially as set forth.

3. The hereinbefore-described method of making magnetic oxid cores forloading-coils, which consists in building or laying up iron plates,ribbon, or wire into a structure of desired form having interstitialspaces between the component layers or turns and extending to theexterior of the mass; in subjecting the said mass to strong heatin anoxidizing-chamber; and in supplying to said chamber an oxygen-containingmedium such as steam which will readily give up oxygen to the iron,substantially as described.

4. The hereinbefore-described method of producing inductance or loadingcoil cores which consists in building, laying up or winding iron platesor wire into an open-work core structure of desired conformation; and inthen converting the substance of said structure without change of forminto a compact and relatively dense mass of artificial magnetic oxid ofsubstantially uniform constitution, by heating or roasting the saidstructure in the presence of an oxygen-supplying mediu m such as steamor carbon dioxid, substantially as described.

5. A core for inductance-coils constituted of non-conducting materialhaving high magnetic permeability,substantiallyas described.

6. A core for inductance or loading coils constituted ofartificially-produced magnetic oxid.

7. A magnetic core for inductance or loading coils constituted offerroso-ferric oxid formed in a compact mass by the substantiallyuniform oxidation of divided iron.

8. A magnetically-permeable core of high electrical resistanceconstituted of artificial magnetic oxid prepared in a solid and compactmass of desired conformation by oxidizing a structure built of plates,ribbons or wires of magnetizable metal into such conformation,substantially as described.

9. A magnetically-permeable and non-conducting core for inductance orloading coils composed throughout or mainly of ferrosoferric oxid in acompact state, and of substantially uniform constitution, prepared byoxidizing a structure consisting initially of iron plates, strips orwire built up or wound into the desired form and size, substantially asset forth.

In testimony whereof we have signed our names to this specification, inthe presence of two subscribing witnesses, this 25th day of November,1901.

JOHN C. LEE. EDWIN H. COLPITTS.

Witnesses:

GEO. WILLIs PIERCE, JAMES E. LYNCH.

